Ball retainer for a reciprocal plunger



United States Patent 2,997,307 BALL RETAINER FOR A RECIPROCAL PLUNGER William .I. Fuhrman, Detroit, Mich., assignor, by mesne assignments,- to the United States of America as represented by the Secretary of the Army Filed May 20, 1960, Ser. No. 30,694

1 Claim. (Cl. 279- 76) This invention relates to devices for retaining a reciprocable plunger within a supporting member.

In machine designs, latches are commonly used which, to perform their functions, must be retained in a supporting member for limited axial displacement therein. One of such applications is in revolver-type machine guns, such as the M39 Automatic Gun, where removal of successive cartridges from a feed belt to the multi-chambered drum is achieved in two steps and at two stations to which the chambers are sequentially indexed during cyclic rotation of the drum. The cartridges in such guns are stripped from the belt by a rammer at one station and partially inserted in the registered chamber during the first ramming step and these first-step-positioned cartridges are completely chambered by the rammer at a subsequent station during the second ramming step.

With this type of feeding, a latch has to be provided which is displaceable to permit the passage of the cartridges to the first-step position and which pops up in back of the cartridge, when in such position, to prevent rearward displacement therefrom and thereby assures con tact by the rammer for the second ramming step. Such a latch is shown in Patent No. 2,900,876 to John G. Brubaker et al. for Combined Rammer and Cam Means for Chambering Cartridges in Revolver-type Guns. However, it is not always possible to locate the latch in the drum support so that it may be retained therein, according to conventional practice, by a laterally disposed pm.

It is an object of this invention to provide ball bearing means for retaining a plunger type latch within a cooperating bore, while permitting limited reciprocation of the latch therein, where it is impractical to retain the latch by a transversal pin because of the location of the bore in the supporting block.

It is another object of this invention to provide such a ball bearing retaining device which permits easy installation and disassembly of the retained member.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a cross-sectional view showing the retainer device disposed for retaining a cartridge latch in the drum support of a revolver-type gun for limited vertical displacement with the latch elevated for preventing rearward displacement of a cartridge from the first-step-ramming position;

FIG. 2 is a view similar to FIG. 1 but showing the latch disassembled from the drum-support; and

FIG. 3 is a cross-sectional view taken along line 33 in FIG. 1.

Shown in the figures is a drum 5 with a plurality of chambers 15 of the type used in the M39 Automatic Gun and a drum support 12 in which a latch 14 is mounted for limited vertical displacement. Latch 14 is disposed in the path of movement of a cartridge 7 when stripped by a rammer 9 from a cartridge belt (not shown) and rammed to a first-step-ramming position. The top of latch 14- is provided with a cam surface 13 which, when contacted by cartridge 7 during movement to the firststep-ramming position, causes the latch to be depressed for uninterrupted passage of the cartridge to such posi-- tion. Latch 14 also includes a plgnger 16 which is slidingly received by a bore 18 which extends downwardly into drum support 12 from the top thereof. Bore 18 is terminated at the bottom by an end wall 20 from which there extends a concentric well 22 for receiving one end of a coiled spring 24. The opposite end of spring 24 contacts the bottom of plunger 16 for biasing latch 14 upwardly in block 12 to a position for blocking rearward displacement of cartridge 7 after the latch is depressed thereby during movement to the first-stcp-raim ming position.

A radial groove 26 is provided vertically along the periphery of plunger 16 between the ends thereof and in the portion of the plunger which is received by bore 18. Groove 26 is terminated at the opposite ends thereof by spherical surfaces 28 each of which has a radius similar to that of the groove. A cylindrical hole 30 extends through drum support 12 parallel to bore 18 and such hole slidingly receives a pin 32 which is terminated at the upper end by a conical portion 34. Extending angularly downward from bore 18 to hole 30 is a cylindrical aperture 36 which provides communication therebetween and such aperture rollingly receives a ball bearing 38 having a radius similar to that of groove 26.

Hole 30 is so spaced from bore 18 that, when ball bearing is installed in aperture 36 and pin 32 is inserted upwardly in hole 30, the ball bearing is pushed by conical portion 34 sufficiently into bore 18 to engage groove 26 and the ball bearing is held against displacement by the engagement thereof between the groove and pin. Whereby, the axial displacement of latch 14 is limited by the contact of ball bearing 38 with the opposite spherical su faces 28 and the rotational displacement of the latch is prevented by the engagement of the ball bearing with aperture 36 and groove 26.

To release latch 14 for disassembly from drum support 12, pin 32 is pressed downwardly until conical portion 34 is clear of aperture 36 whereby ball bearing 38 is free to roll down aperture 36 through the force of gravity into a junction 37 thereof with hole 30 to be pocketed therein clear of groove 26. Hole 30 is preferably of smaller diameter than ball bearing 38 so that it cannot enter such hole. Latch 14 is reassembled by inserting plunger 16 thereof into bore 18 for registry of groove 26 with aperture 36 and then pressing upwardly on pin 32 whereby conical section 34 cams ball bearing 38 upwardly along the aperture and into the groove. Continued upward displacement of pin 32 secures ball bearing 38 in groove 26 so that latch 14 is slidingly retained in drum support 12.

From the foregoing it is clearly apparent that there is provided herein a device for retaining a reciprocating latch within a supporting member where it is more advantageous to provide a mounting hole which is disposed parallel rather than transversal to the reciprocation of the retained member.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claim is intended to include such variations.

I claim:

A device for retaining a latch with a plunger in a member having a vertical bore for slidingly receiving the plunger so that the latch is retained in the member for limited vertical reciprocation therein, said device including a peripheral groove disposed vertically in the plunger between the ends thereof, a pair of spherical. surfaces terminating the top and bottom ends of said groove, a ball bearing having a diameter less than that of the bore, a cylindrical hole extending through said member parallel to the longitudinal axis of the bore, said hole having a diameter smaller than that of said ball bearing, a cylin- Pafented Aug. 22, 1961 d a aperture tendin n ularly q n n r n. lbs bore to form a junction with said hole, the diameter of said aperture being similar to that of said ball bearing so that said ball bearing is rollingly received by said said ball bearing upwardly in said aperture, and sa-id hole 1 being spaced from the bore a distanceless than the diameter of said ball bearing, whereby said ball bearing is displaceable by said pin into the bore sufficiently to be received by said groove for contact by one of said pair of spherical surfaces to limit the vertical reciprocation of the plunger.

References Cited in the file of'this patent UNITED. STATES. PATENTS 1,683,501 Tobeler; Sept. '4, 1928 1,969,426 Ross Aug. 7, 1934 2, 54 2 8, enn ll, f:-- --.-r--.--a- S p 1953 

